Uintacrinus anglicus Rasmussen from the Upper Cretaceous Flamborough Chalk Formation of Yorkshire: implications for the position of the Santonian-Campanian boundary

Abstract

Calyx plates of the crinoid Uintacrinus anglicus are recorded from the top and bottom of a 5 m interval, 4 m above the disappearance of calyx plates of the crinoid Marsupites testudinarius within the Flamborough Chalk Formation at Danes Dyke in North Yorkshire, UK. The U. anglicus Zone, as used here, comprises the interval from the disappearance of M. testudinarius to the disappearance of U. anglicus calyx plates, and therefore includes, but does not comprise, the total range of the index species. Two subzones are recognized in the M. testudinarius Zone; a lower subzone characterized by smooth Marsupites calyx plates and an upper subzone characterized by variably ornamented Marsupites calyx plates. A provisional study of the belemnite indicates the Gonioteuthis granulataquadrata appears in the highest part of the M. testudinarius Zone. The 1983 Copenhagen symposium on Cretaceous stage boundaries proposed that the base of the Campanian Stage should be drawn at a level close to the appearance of G. granulataquadrata. Consequently, the extinction of M. testudinarius is used to define the base of the Campanian here and U. anglicus Zone is placed in the basal Lower Campanian.